1. Field of the Invention
The present invention generally relates to a power supply circuit utilized as constant power supply, and specifically relates to such power supply circuits that switch between an active mode and a sleep mode.
2. Description of the Related Art
In this technology area, there are some types of power supply circuits. In one type, consumption current is large for improving PSRR (ripple removing rate) and load transient response. In another type not-requiring high speed response, consumption current is lowered.
For example, a power supply circuit as shown in FIG. 5 has a voltage regulator as a series regulator. The power supply circuit has a circuit having a large current consumption for improving PSRR or load transient response. Sometimes, this power supply circuit is used for cellular phones having an active mode (operating mode) and a sleep mode (waiting mode). In such situation, while the cellular phone is in the sleep mode that does not require high speed response, the power supply circuit consumes the current wastefully.
One technology dealing with this issue is disclosed in Japanese Patent No. 2,734,551, in which a high speed amplifier having large current consumption and a slow speed amplifier having low current consumption are switched.
This technology, however, needs to have both the high speed amplifier and the low speed amplifier, making its chip area larger and increases cost.